a cold and backwjird spring after corn-planting increases injury to the 

 seed and the young plant by wireworms, seed-corn maggots, and the 

 corn root-aphis; and a midsummer drouth greatly increases the effect, 

 if not the amount, of injury by chinch-bugs, white-grubs, and the corn 

 root-worm. 



General Effects of Insect Injury. 



With few exceptions, the effects of injury to corn by insects, where 

 they do not amount to a total destruction of the plant, may be compared 

 to the effects of simple starvation. Anything which lessens the store 

 of food laid up in the corn kernel for use in germination and early growth, 

 or damages seriously the roots or the leaves, or draws away the sap 

 before it has served its purpose in the plant, practically amounts to a 

 diminution of the available food supply. An impoverished soil, very 

 dry weather, the sapping of the cells and vessels of the plant by sucking 

 insects, destruction of any considerable part of its roots, and the dead- 

 ening or destruction of any large percentage of its leafage, all have 

 similar consequences, which may be classed as starvation effects, and 

 when two or more of them coincide, each serves, of course, to intensify 

 the effects of the others. 



One common result of these starvation injuries to corn is the failure 

 of the plant to form the ear; the stalk itself, perhaps, making a fairly 

 vigorous growth, but remaining barren, and hence useless except for 

 fodder. Injury to the roots, if continuous and severe, has, however, 

 another effect, of a more special character, in so weakening the hold of 

 the plant on the earth that the stalk readily falls after it has become top- 

 heavy with growth, and is not able to rise again. This happens after 

 soaking rains have softened the ground, especially if accompanied by 

 heavy winds. It is sometimes a consequence of the destruction of the 

 roots by the corn root-worm and the white-grubs, and is sometimes 

 due to chinch-bugs, which, by sucking the sap from the base of the 

 stem, prevent the formation of the strong "brace-roots" — the upper 

 circle of roots — put forth during the last stages of the growth of the 

 stalk. Actual loss of roots sometimes also delays the development of 

 the plant, acting in this respect like an unusually cool summer. Thus, 

 a field infested by grubs or root-worms may remain green after unin- 

 jured fields are practically ripe. Such backward fields are especially 

 exposed to injury by frosts, and hence are likely to yield an unusual 

 amount of soft corn. 



Besides this class of general injuries, which diminish the vitality and 

 lessen the size or delay the growth of the whole plant, there remain only 

 the more local injury to the ear, caused almost wholly by the caterpillar 

 known as the corn root-worm, and the damage done to the ear in the 

 crib or to the kernel in the bin by the weevils and other insects of similar 



